Perfectly legal - there is no specific law about how old a baby sitter needs to be
However, I would be worried about leaving a 14 year old home with his sister (who is how old?) until 11pm at night. Is there a neighbour who could at least keep an ear out for them?
My daughter is 10. My place of work is only 5 minutes walk and I have a neighbour whom is a friend that is on call to them untill I return.They only have to call.
Thankyou for your help and advise it has made me feel easier. It is a one off situation as i will only leave my children with their father as a rule as only normally work week end but unfortunately he is working away this week. Thankyou again.